Paul Gilmartin wrote: >z/OS shirks the issue by making user address spaces non- dispatchable >during a leap second.
That's one option, the less commonly chosen one. You would choose this option if you need your z/OS environment to have highly accurate time that fully reflects the leap second the instant it occurs. You might be in this situation if your z/OS environment directly supports a financial trading exchange open across UTC leap second insertion, for example. [Maybe. The exchange presumably would have to halt trading for one second.(*)] This one second "pause the world" behavior is to avoid creating UTC time stamps that would be duplicates and/or incomprehensible to practically the world's entire catalog of leap second ignorant software, possibly including parts of z/OS itself. The other, more popular option is to steer across the leap second. That's a Server Time Protocol option, and it takes about 7 hours to adjust to the one second delta. >z/VM? Short answer: use the popular option (steer across). Longer and fantastic answer: see Alan Altmark's excellent article. http://www.vm.ibm.com/devpages/altmarka/vmleap.html (*) This scenario vaguely reminds me of Japanese ATM networks (in convenience stores typically) that publicly advertise 12:01 AM to 11:59 PM service availability. I think they still do that. For whatever reason(s) the network needs a brief scheduled outage across midnight every night, and in Japan at least that 60 or 120 second daily planned outage is advertised lest anyone panic that their first ATM transaction attempt didn't work. It's entirely possible that 1 or 2 minute planned outage is no longer technically required, but changing the published SLA might be..."difficult." :-) - - - - - - - - - - Timothy Sipples I.T. Architect Executive Digital Asset & Other Industry Solutions IBM Z & LinuxONE - - - - - - - - - - E-Mail: [email protected] ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
